1. Field of the Invention
The subject invention relates to solid state circuit-breaker switches, and more particularly to solid state circuit-breaker switch devices having a first switch arranged between a load and a positive terminal and second switch arranged between the load and a return terminal.
2. Description of Related Art
Hybrid electric vehicles utilize high voltage direct current power management and distribution. Solid state circuit-breaker (SSCB) switches are used in conventional power distribution systems to replace traditional electromechanical circuit-breakers. Their main functions are to distribute power to different loads. Compared to traditional electromechanical circuit-breakers, SSCB switches provide relatively fast response time, eliminate arcing during turn-off transients and bouncing during turn-on transients, and do not suffer performance degradation as a result of repeated fault isolation events. SSCB switches also have lower weight and size than traditional electromechanical circuit-breakers. SSCB switches are also capable of providing advanced protection and diagnostics, more efficient power architectures and packaging techniques.
In order for a SSCB switch to meet the requirements of hybrid vehicles, the SSCB switch needs to (a) have low conduction losses during steady-state operation, (b) have up to 1000% overload capability to meet current to time trip curve characteristics, and (c) be able to tolerate high operating voltages due to inductive spikes that can occur in the system.
Power metal-oxide-semiconductor field-effect-transistors (MOSFETs) are a good choice for such applications due to their low conduction loss (low RDS-ON). Moreover, because of the positive thermal coefficient associated with their on-state resistance, MOSFETs may be easily paralleled to achieve a desired conduction loss during steady-state operation. However, during overload transient conditions MOSFETs may be subject to current unbalance that can cause the device to exceed its peak current and/or continuous thermal rating.
Silicon carbide (SiC) MOSFETs offer reduced conduction losses due to small RDS-ON. However, their relatively small size in comparison with silicon devices for the same rated power increases their heat flux and results in a higher thermal impedance of the packaged device. Moreover, during turn-off events SiC MOSFETs can experience large overvoltage spikes due to their very fast turn-off time and can require additional voltage clamping devices, e.g. snubbers and Zener diodes.
While suitable for their intended purpose, there is a need for improved SSCB switches. There also remains a continuing need for SSCB switches that are easy to make and use. The present invention provides a solution to these problems.